When milk is processed into dairy or other food products there are a number of properties of the milk that are desirous, depending on the product to be produced, e.g. low tendency to produce fouling of equipment, good emulsification properties and high heat stability. Specifically, for production of butter a high yield of butter from the cream is desirous, and when producing liquid acidified milk drinks, a low viscosity may be desired.
Milk used for production of dairy products is very often heat treated, e.g. by pasteurisation. A well-known problem when heat treating milk is fouling of the heating surfaces, i.e. that milk solids are deposited on the surfaces decreasing the heat transfer rate. This problem is known e.g. with plate heat exchangers and in evaporators. Fouling is also an important problem in relation to a number of other dairy processes, e.g. membrane filtration. Fouling is related to the wetting of the, usually hydrophilic, surfaces of processing equipment, and the wetting properties are largely determined by surface tension. According to Paramalingam et al.: On the fouling of falling film evaporators due to film break-up (2000), Food and Bioproducts Processing, 78, pp. 79-84, surface tension is an important factor in fouling of falling film evaporators. Furthermore, it has been shown that the higher the contact angle, the less material is deposited on heating surfaces during heat treatment of milk (O. Santos et al. (2004): Effect of surface and bulk solution properties on the adsorption of whey protein onto steel surfaces at high temperature. In: Santos, O.: Whey protein adsorption and aggregation on modified stainless steel surfaces in relation to fouling, Doctoral thesis, Lund University, Lund, Sweden). The contact angle is increased when the surface tension of milk is decreased. Fouling decreases efficiency of processing equipment and increases the need for cleaning of the equipment, leading to lost production time. There is a desire to decrease the rate of fouling of dairy process equipment. Fouling is often caused by deposition of milk proteins, e.g. beta-lactoglobulin, on solid surfaces, and may be reduced by replacing milk proteins with other substances at the liquid/solid interface.
Milk comprises phospholipids. The phospholipids are associated with the milk fat due to its non-polar, lipophilic properties. Phospholipids may be hydrolysed by phospholipase into lysophospholipid, which may in turn be hydrolysed by a lysophospholipase (phospholipase type B). WO 00/54601 (Novozymes A/S) discloses a method for producing cheese, comprising treating the cheese milk with a phospholipase.